1. Field of the Invention
The present invention relates to a mask for hardening a sealant and a method of manufacturing a flat display device using the mask, and more particularly, to a mask for hardening a sealant, which mask can suppress sealing failure caused by a deviation in exposure according to a region of the sealant, and a method of manufacturing a flat display device using the mask.
2. Description of the Related Art
A flat display device, such as an organic light-emitting display device, due to its operating nature, can be made to have thin thickness and flexibility, thus being much researched.
In the organic light-emitting display device, however, a light-emitting portion deteriorates by permeation of moisture and water. To prevent the permeation, the organic light-emitting display device needs an encapsulating structure which protects the light-emitting portion by sealing the light-emitting portion.
The encapsulating structure is usually a structure which covers a glass substrate where the light-emitting portion is formed with the encapsulating substrate, and which seals a gap between the glass substrate and the encapsulating substrate with a sealant, such as frit. That is, frit is applied around the light-emitting portion formed on the glass substrate, is covered thereon with the encapsulating substrate, and is then hardened by laser irradiation, thereby completing sealing.
When the frit enclosing the light-emitting portion, that is, the sealant, is hardened by laser irradiation, a large deviation in the amount of energy for laser irradiation from region to region may result in sealing failure. In other words, an insufficient amount of energy may hinder proper sealant hardening, leading to sealing failure; whereas an excessive amount of energy may generate a large amount of bubbles on the surface of the sealant, also resulting in sealing failure.
Therefore, the laser has to be uniformly irradiated across all the regions of the sealant. However, the problem is that the amount of laser irradiation inevitably differs between a straight line portion and a corner portion given that the sealant is approximately in a square shape. In other words, the sealant generally encloses the light-emitting portion formed on the glass substrate in the shape of a square. Thus, during hardening of straight line portions corresponding to four sides, a laser irradiator can uniformly irradiate the laser onto these portions while moving at a constant speed. During hardening of corner portions corresponding to connecting portions between the four sides, however, the laser irradiator slows down when compared to hardening the straight line portions, thereby increasing the amount of laser irradiation. As a result, when the amount of laser irradiation is set based on the straight line portions, bubbles are generated on the surface of the sealant due to the excessive amount of laser irradiation onto the corner portions, leading to sealing failure.
Accordingly, there is a need for a method for solving the foregoing problem by reducing deviation in the amount of laser irradiation from region to region in the sealant.